Which division of the skeletal system includes bones of the skull, vertebral column, and rib cage?

Correct Answer: A

Rationale: The skeletal system is divided into two main parts: the axial skeleton and the appendicular skeleton. The axial skeleton includes the bones that form the central axis of the body, such as the skull (which protects the brain), the vertebral column (which protects the spinal cord), and the rib cage (which protects the heart and lungs). The appendicular skeleton, in contrast, includes the limbs and girdles. Long bones and irregular bones are types of bones, not divisions of the skeletal system, making 'Axial skeleton' the correct choice.

Correct Answer: A

Rationale: During muscle contraction, the sliding filament theory explains that myosin filaments slide along actin filaments to shorten the sarcomere and generate force. Myosin heads bind to actin, pulling it inward. Troponin and tropomyosin regulate this process, while collagen is structural, not contractile, making 'Myosin' the correct answer.

Correct Answer: B

Rationale: The appendicular skeleton, including limbs and girdles, is designed for movement and locomotion. Bones like the femur and humerus enable walking and arm motion, supported by the pelvic and pectoral girdles. Protection of organs is an axial skeleton role, making 'Facilitating movement and locomotion' the correct answer.

Correct Answer: C

Rationale: Acetylcholine (ACh) is released by the motor neuron at the neuromuscular junction, crossing the synaptic cleft to bind to muscle fiber receptors, triggering an action potential for contraction. It does not inhibit, relay sensory data, or degrade fibers, making 'Transmitting signals from the motor neuron to the muscle fiber' the correct answer.

Correct Answer: A

Rationale: Creatine phosphate stores high-energy phosphate bonds in muscle cells. During contraction, it transfers its phosphate to ADP, regenerating ATP to power myosin heads. Glycogen is a glucose store, myoglobin holds oxygen, and lactic acid is a byproduct, making 'Creatine phosphate' the correct answer.